Pharmacological or dietary treatments that perturb calcium metabolism cause rats to ingest large volumes of salt. This project will delineate (1) the physiological basis of this interaction, and (2) the contribution of calcium metabolism to other rodent models of salt intake. Specifically, the involvement of calcium-regulating hormones in the control of salt intake wiLL be assessed by measuring mineral intake and balance in rats with these hormones removed by parathyroidectomy, thyroidectomy, or dietary vitamin D deficiency. In some rats, plasma calcium wiLL be held constant by calcium infusions in order to dissociate any direct effects of calcium-regulating hormones from their effects on plasma calcium. To investigate the relationship between calcium metabolism, salt intake and blood pressure, these variables will be compared in rats treated with calcium blockers, or with genetic hypertension. tHe contribution of calcium to the increase in salt intake associated with reproduction will be studied by examining salt and calcium intake during pregnancy and lactation. Finally, the possible contribution of perturbations in calcium metabolism to the increased salt intake produced by adrenalectomy will be assessed by mineral intake and balance studies. This work will provide a firm foundation for a new rodent model of salt intake, which promises to be directly relevant for understanding excess salt intake and its deleterious consequences in humans.